Process for making smokeless powder



United States Patent PROCESS FOR MAKING SMOKELESS POWDER John J. ONeill,Jr., Roxana, IlL, assignor to Olin Mathieson Chemical Corporation, acorporation of Virginia N0 Drawing. Filed Feb. 24, 1951, Ser. No.212,667

Claims. (CI. 52-20) This invention relates to the manufacture of powderand particularly to propellent powder.

In the manufacture of propellent powders it is sometimes desirable inorder to modify the characteristics of the powder to incorporate thereinfinely subdivided water insoluble compounds that are also insoluble inthe usual nitrocellulose solvents. The need for such a modifying agentis disposed, for example, by Crawford in. US. Patent 2,440,327, issuedApril 27, 1948, in which it is pointed out that a dye or carbon blackuniformly dis persed throughout the powder grain prevents what is knownin the trade as fissures or worm holes resulting from radiant ignitionin transparent grains. Bruce and Klein in US. 2,499,295, issued February28, 1950, disclose a method for incorporating carbon black in powder inwhich the carbon black is dispersed in a plasticizer for nitrocellulose,this dispersion is then added to a suspension of nitroglycerine andnitrocellulose in water, and after addition of the remainingingredients, the mass in dewatered and the resulting wet paste dried.The dry material is then colloided in the usual manner by Working ondifferential speed rolls at relatively high temperature. This method ofincorporation, although allegedly securing uniform distribution of thecarbon black through the powder, has the disadvantages that it is notalways desirable to include such a plasticizer in the powder compositionand the method of colloiding by working on rolls is relativelyhazardous. Olsen, Tibbitts, and Kerone in US. Patent 2,027,114, issuedJanuary 7, 1936, disclose an eflicient relatively safe process of makingpowder in which nitrocellulose and a solvent for the nitrocellulose areagitated in a non-solvent vehicle containing a protective colloid withsubsequent removal of the solvent by vaporization or the like to formthe globular powder grains. Insoluble modifiers have been incorporatedin the powder grains by merely adding the modifier to the agitated bath,but this method has the disadvantages that a not entirely uniformdistribution of the modifier was obtained and a large portion of themodifier would not even enter the powder grain, so that control of thecomposition of the grain was practically impossible. Attempts have alsobeen made to incorporate such modifiers in powder grains by firstdissolving the nitrocellulose in the solvent to form a lacquer,incorporating the modifier and other ingredients therein, and thenadding the mixture to the non-solvent with agitation. This method hasthe disadvantage that appreciable amounts of solvent are necessary toprovide a flowable lacquer, making the control of grain size difficultand requiring additional handling equipment.

Such a process of forming powder grains in a nonsolvent dispersion hasnumerous advantages and it is an object of this invention to provide animprovement thereon permitting the incorporation of such pulverulentinsoluble modifiers uniformly throughout the powder grains in controlledamounts. Another object of this invention is to provide an improvedprocess for the 2,945,751 Patented July 19, 1960 incorporation insmokeless powder of a modifier which is relatively insoluble in waterand the ordinary nitrocellulose solvents. Still another object is toprovide an improved process for the manufacture of powder having theadvantages attending the formation of powder grains in aqueous mediumand permitting the uniform incorporation in the powder grain ofcontrolled amounts of insoluble modifiers.

In accordance with this invention, these and other objects areaccomplished by wetting the insoluble modifier with a volatile solventfor the nitrocellulose before addition of the modifier to a non-solventbath in which the nitrocellulose and solvent therefor are agitated toform the powder grains. In carrying out the process, the nitrocelluloseor smokeless powder base with or without nitroglycerine is usuallysuspended in a non-solvent vehicle such as water bath by agitation. Thepulverulent insoluble modifier is dispersed in a volatile nitrocellulosesolvent, i.e. having a boiling temperature less than that of thenon-solvent vehicle and relatively immiscible or only partially solublein the non-solvent vehicle, and the resulting dispersion is then addedto the non-solvent vehicle with the agitation being continued until thenitrocellulose is dissolved in the solvent. A protective colloid such asdextrin, starch, gum arabic, or those derived from animal proteins, andthe like, is then added to prevent the globules of the so-formednitrocellulose lacquer emulsion from sticking together or to the sidewalls of the vessel. When as a result of agitation the globules in theemulsion have attained the desired particle size, the solvent isvaporized to provide the resultant hardened grains of powder. Theresultant powder grains contain uniformly dispersed thereinsubstantially the entire amount of such modifier added to the bath. Ifdesired the modifier may be wet with or dispersed in only a portion ofthe solvent utilized in forming the powder grains, but in any event theinsoluble modifier should be thoroughly wet with the solvent prior toits addition to the non-solvent vehicle.

Any desired insoluble modifier, i.e. substantially insoluble in thenon-solvent vehicle and nitrocellulose solvent, may be added to thepowder, uniformly throughout the powder grains and in controlled amountsin accordance with this process. For example, the powder grains may havethus incorporated therein carbon black to provide the desired opacityand prevent undesirable radiation ignition, or modifiers such ascyclomethylenetrinitramine or even aluminum dust to provide additionalenergy, or calcium carbonate for increased stability, or powdered iron,iron oxide, red lead, lead chromate, or lead sulphide for controllingthe burning characteristics, and the like. The nonsolvent vehicle,variously referred to herein as the non-solvent or the vehicle," shouldhave substantially no solvent power for either the powder base, or thesolvent for the nitrocellulose, or the insoluble modifier. Because ofits availability and low cost water is preferred as the non-solvent,although any other suitable non-solvent may be employed. Any suitablenitrocellulose solvent substantially insoluble in the non-solventvehicle and having a boiling temperature below that of the vehicle maybe utilized, as for example ethyl acetats, methyl ethyl ketone, or thelike. Other soluble ingredients, such as deterrents and the like may beadded to the powder in accordance with the usual practice.

In order that the invention may be further clarified following is anexample illustrating a typical embodiment of the invention. Two hundredfifty parts of nitrocellulose having a nitrogen content of 12.6% wasagitated with 4100 parts of water at about C. to form an aqueous slurry.A suspension of carbon black in ethyl acetate was separately prepared byfirst thoroughly mixing 0.562 parts of carbon black with 100 parts ofethyl acetate. This mixture of carbon black and ethyl acetate was thenadded to 1000 parts more of ethyl acetate, and the resultant dilutecarbon black-ethyl acetate mixture was agitated to insure uniformdistribution of the suspended particles of carbon black. Thirty six andonetenth parts of dinitrotoluene and 2.8 parts of ethyl centralite werethen added to the carbon black-ethyl acetate mixture. When thedinitrotoluene and the ethyl centralite were dissolved, the resultingmixture was then added to the nitrocellulose slurry while the slurry wasunder agitation. The temperature was raised to 68 C. and the completecharge agitated for one hour at which time the nitrocellulose wasdissolved. Twenty-five parts of a protective colloid of the type derivedfrom animal protein dispersed in 150 parts of water was then added andthe agitation was continued until the nitrocellulose solution was formedinto globules of the desired size. One hundred twenty-five parts ofsodium sulfate dissolved in 300 parts of water was added over a one hourperiod and agitation continued for an additional 3 hours. The globuleswere then hardened to form powder grains by removal of the ethyl acetateduring continuous agitation and heating up to about 99 C. in accordancewith the practice set forth in U. S. Patent 2,027,114 referred to,hereinbefore. The resultant powder grains were composed of 87.7nitrocellulose, 11.0% diinitrotolueue, 0.3% carbon black, and 1.0% ethylcentralite, with the carbon black being uniformly dispersed throughoutthe grains. Substantially the entire amount of carbon black originallyadded to the agitated slurry was in the powder grains. In thoseinstances, when the carbon black was added without first being wettedwith the ethyl acetate only a relatively small fraction of the carbonblack added to the slurry appeared in the powder grains and the residualcarbon black in the water was lost when the powder was filteredtherefrom.

In the following embodiment there is illustrated a method forincorporating an energizing modifier, such ascyclotrimethylenetrinitramine, in the powder grains. To 1000 parts ofwater at a temperature of about 50 C. was added 75 parts ofnitrocellulose having a nitrogen content of 12.3% and the mixtureagitated to form a slurry. About 94 parts ofcyclotrimethylenetrinitramine was then suspended in about 375 parts ofethyl acetate having dissolved therein about 0.94 part of diphenylamineas a stabilizer and about 19 parts of dibutyl phthalate as a deterrentand the resulting mixture was added to the nitrocellulose-water slurrywith agitation and the mixture heated to 68 C. When the nitrocellulosewas all dissolved, fifty parts of protective colloid derived from animalprotein was then added and the mixture agitated until the resultingglobules of nitrocellulose lacquer attained the desired particle size.Twenty-five parts of sodium sulfate dissolved in 50 parts of water werethen added. After three hours of agitation the temperature was thengradually raised to about 99 C. to effect removal of the ethyl acetateand harden the powder grains. Upon filtering the powder grains from theaqueous bath, it was found that the cyclotrimethylenetrinitramine wasuniformly distributed throughout the nitrocellulose of the grain. Thecomposition was about 50% cyclotrimethylenetrinitramine, about 40%nitrocellulose, about dibutyl phthalate, and about 0.5% diphenylamine.

In still another embodiment, 12.1 parts of nitrocellulose having anitrogen content of 12.6% were added to 430 parts of water and themixture was agitated and heated to a temperature of 50 C. In a separatevessel, 68.8 parts of crystalline cyclotrimethylenetrinitramine weresuspended in 137.5 parts of ethyl acetate having dissolved therein 0.086part of diphenylamine. The suspension of thecyclotrimethylenetrinitramine in the ethyl acetate was then added to thewater bath of nitrocellulose and the mixture heated to 65 C. withcontinued agitation. After about 1 /2 hours, at which time thenitrocellulose was all in solution and the cyclotrimethylenetrinitraminewas uniformly distributed through the nitrocellulose solution, 2.2 partsof protective colloid derived from animal protein dispersed in 30 partsof water was then added to the agitated nitrocellulose solution. Afterapproximately /4 of an hour of continued agitation, the globules ofnitrocellulose solution had attained the desired size and 12.5 parts ofsodium sulphate dissolved in 30 parts of Water was slowly added to themixture which was then agitated for about 5% hours. When the. sodiumsulphate is added an osmotic action takes place tending to remove anywater dissolved in the globules of nitrocellulose solution and thus, thefinal density of the powder grain is increased. If no sodium sulphate,or equivalent material, is utilized, the powder grains tend to have agreater porosity. The bath was then heated to raise the temperatureslowly to about 99 C. to drive oil the solvent and harden the globulesinto powder grains. The hardened powder analyzed aboutcyclotrimethylenetrinitramine, about 20% nitrocellulose, and about 0.1%diphenylamine. The crystals of cyclotrimethylenetrinitramine weresubstantially uniformly dispersed throughout the nitrocellulose of eachgrain.

In each of the above examples the pulverulent insoluble modifier had aparticle size substantially less than that passing through a standard100 mesh U. S. sieve. Although insoluble modifiers having substantiallygreater particle size may be incorporated in the powder grains inaccordance with this process, it is preferred that the particle size besuch as to pass through a standard U.S. 100 mesh sieve. The powder basemay be fibrous or colloided nitrocellulose, and may includenitroglycerine or other ingredients, and any base suitable for smokelesspowder may be utilized.

From the foregoing specific examples it will thus be apparent thatwidely divergent amounts of pulverulent insoluble modifiers may beuniformly dispersed in powder grains and in controlled amounts inaccordance with this invention and the desired objects and advantagesare thereby attained. While the foregoing embodiments have been setforth in detail, it is to be distinctly understood that manymodifications and variations will naturally present themselves to thoseskilled in the art without departing from the spirit of this inventionor the scope of the appended claims.

Having thus described the invention, what I claim and desire to secureby Letters Patent is:

1. In the art of makingpowder by a process in which a smokeless powderbase dissolved in a solvent therefor is agitated in a non-solventvehicle containing a protective colloid and the solvent is subsequentlyremoved to yield hardened powder grains, the step of incorporatingtherein a pulverulent modifier insoluble in said solvent and vehiclewhich comprises first wetting said insoluble modifier with a solvent forthe smokeless powder base which has a boiling point less than that ofthe vehicle, and then introducing said wet insoluble modifier into saidvehicle.

2. In the art of making powder by a process in which a smokeless powderbase dissolved in a solvent therefor is agitated in a water bathcontaining a protective colloid and the solvent is subsequently removedto yield hardened powder grains, the step which comprises introducinginto said water bath a pulverulent modifier insoluble in but wet with asolvent for said smokeless powder base which has a boiling point lessthan that of water.

3. The process of claim 1 wherein said modifier is carbon black.

4. The process of claim 1 wherein said modifier iscyclotrimethylenetrinitramine.

5. The process of claim 1 wherein said nonsolvent vehicle containssodium sulfate.

References Cited in the file of this patent UNITED STATES PATENTS 6OTHER REFERENCES Davis: The Chemistry of Powder and Explosives," vol.II, published in NY. (1943), by John Wiley and Tibbitts et July 1934Sons, Inc., London, Chapman and Hall, Ltd., pages 327, 015M! et a1. 9, 5and Olsen Aug'11'1942 Hackh's Chemical Dictionary (Grant, 3rd edition),Herwg 5, 1946 pub. 1944, by the Blakiston 00., Philadelphia, TorontoBI'HCQ et a]. Feb. 28, 1950 (reprinted 1950), page 653.

Attesting Oficer UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No. 25945351 July 19 1960 John J. O"Neil1 Jr.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring o orrection and that the saidLetters Patent should read as corrected below.

Column l line 22 for "disposed" read disc losed column 3 line 27, for"87.7 read M 87.7% l1ne 73 for "part" read parts Signed and sealed this3rd day of January 1961,

(SEAL) Atteet:

A AXLINE ROBERT C. WATSON Commissioner of P 81161118

1. IN THE ART OF MAKING POWDER BY A PROCESS IN WHICH A SMOKELESS POWDERBASE DISSOLVED IN A SOLVENT THEREFOR IS AGITATED IN A NON-SOLVENTVEHICLE CONTAINING A PROTECTIVE COLLOID AND THE SOLVENT IS SUBSEQUENTLYREMOVED TO YIELD HARDENED POWDER GRAINS, THE STEP OF INCORPORATINGTHEREIN A PULVERULENT MODIFIER INSOLUBLE IN SAID SOLVENT AND VEHICLEWHICH COMPRISES FIRST WETTING SAID INSOLUBLE MODIFIER WITH A SOLVENT FORTHE SMOKELESS POWDER BASE WHICH HAS A BOILING POINT LESS THAN THAT OFTHE VEHICLE, AND THEN INTRODUCING SAID WET INSOLUBLE MODIFIER INTO SAIDVEHICLE.